A biosensor may be a device for the detection of an analyte that combines a biological component with a physicochemical or physical detector component.
Magnetic biosensors may use the Giant Magnetoresistance Effect (GMR) for detecting biological molecules being magnetic or being labeled with magnetic beads.
In the following, biosensors will be explained which may use the Giant Magnetoresistance Effect.
WO 2005/010542 discloses the detection or determination of the presence of magnetic particles using an integrated or on-chip magnetic sensor element. The device may be used for magnetic detection of binding of biological molecules on a micro-array or biochip. Particularly, WO 2005/010542 discloses a magnetic sensor device for determining the presence of at least one magnetic particle and comprises a magnetic sensor element on a substrate, a magnetic field generator for generating an AC magnetic field, a sensor circuit comprising the magnetic sensor element for sensing a magnetic property of the at least one magnetic particle which magnetic property is related to the AC magnetic field, wherein the magnetic field generator is integrated on the substrate and is arranged to operate at a frequency of 100 Hz or above.
US 2005/035757 discloses a magnetoresistive sensing device having a substrate with a layer structure for supporting a fluid. The layer structure has a first surface area in a first level and a second surface area in another second level and a magnetoresistive element for detecting the magnetic field of at least one magnetic particle in the fluid, the magnetoresistive element being positioned near a transition between the first and second surface area and facing at least one of the surface areas.
WO 2005/111596 discloses a system for distinguishing a specific binding from a less specific binding between at least one magnetic nanoparticle and a surface of another entity by applying a magnetic field and detecting a physical parameter relating to magnetic nanoparticle rotational or motional freedom while the magnetic nanoparticle is attached to the surface. The system may be applied to in-vivo and in-vitro biomolecular diagnostics. The sensor combines in one sensor the detection of magnetic particles or labels and determination of the binding quality and the properties of magnetic particles or labels which are bound to the surface of another entity.
However, sufficient accuracy of measurement results may still be problematic under undesired circumstances.